Lens dyeing method and lens dyeing aparatus: dyeing lenses to give a continuous color density gradient

Abstract

A dyeing method for dyeing plastic lenses or the like employed as lenses for eye glasses and exhibiting excellent dyeability. The lens is dipped into a dyeing solution while being moved by a combination of a small-amplitude short-cycle time up and down reciprocating motion superimposed on a large-amplitude long-cycle time up and down reciprocating motion. The lens is minutely oscillated according to the small-amplitude short-cycle time up and down reciprocating motion while being periodically moved up and down in the dyeing solution according to the large-amplitude long-cycle time up and down reciprocating motion. The lowest position of the lens obtained by the large-amplitude long-cycle time up and down reciprocating motion is raised gradually. Also disclosed is a dyeing apparatus which is used to carry out that dyeing method.

We claim: 
     
       1. A lens dyeing method for dyeing a lens in such a manner that a continuous color density gradient occurs on surfaces of said lens, said method comprising the steps of dipping the lens into a dyeing solution while periodically changing the position of the lens according to a combination of a first mode of motion superimposed on a second mode of motion, the first mode of motion comprising an up and down reciprocating motion having a first amplitude from a lowest position to a highest position of said first mode of motion and a first cycle time, the second mode of motion comprising an up and down reciprocating motion having an amplitude from a lowest position to a highest position of said second mode of motion which is larger than said first amplitude of said first mode of motion, and a cycle time which is longer than said first cycle time of said first mode of motion, said combination of superimposed modes of motions being conducted such that said lens is minutely oscillated up and down according to said first mode of motion, while being periodically moved up and down in the dyeing solution according to said second mode of motion, and said second mode of motion is wholly shifted upward by a predetermined distance for each cycle of said second mode of motion thereby raising the lowest position reached by said lens during each successive down motion according to said second mode of motion for each cycle of said second mode of motion, to alter the position of a boundary defined between a dipped portion and a non-dipped portion on the surfaces of said lens.   
     
     
       2. A lens dyeing method according to claim 1, wherein said predetermined distance is constant. 
     
     
       3. A lens dyeing method according to claim 1, wherein said predetermined distance is constant. 
     
     
       4. A lens dyeing method according to claim 1, wherein said lens has formed thereon a hard coating film comprising an organic silicone compound. 
     
     
       5. A lens dyeing method according to claim 1, further comprising the steps of dipping the entirety of said lens into said dyeing solution for a predetermined period of time. 
     
     
       6. A lens dyeing method according to claim 5, wherein said dipping of the entirety of said lens is conducted prior to said step of periodically changing the position of the lens. 
     
     
       7. A lens dyeing method according to claim 5, wherein said step of periodically changing the position of the lens is conducted before and after said dipping the entirety of said lens. 
     
     
       8. A lens dyeing method for dyeing a lens in such a manner that a continuous color density gradient occurs on surfaces of said lens, said method comprising the steps of dipping the lens into a dyeing solution while periodically changing the up and down position of the lens according to a combination of a first mode of motion superimposed on a second mode of motion ,the first mode of motion comprising an up and down motion having a relatively small amplitude and a relatively short cycle time, the second mode of motion comprising an up and down motion having a relatively large amplitude and a relatively long cycle time, said combination of superimposed modes of motions being conducted such that said lens is moved up and down according to said first mode of motion, and said second mode of motion is holly shifted upward by a predetermined distance for each cycle of said second mode of motion thereby raising a lowest position reached by said lens during each successive down motion according to said second mode of motion for each cycle of said second mode of up and down motion, to alter the position of a boundary defined between a dipped portion and a non-dipped portion on the surface of said lens.